Visibility Monitoring

Visibility Monitoring

Visibility

The Nephelometer
is used as a standard part of Air quality monitoring networks in many
parts of the world, including state EPA’s in Australia and the U.S.A.

The Nephelometer measures the scattering of light,
thus it can detect the distance the naked eye can see (in km). This
monitoring is extremely useful when reporting data to the general public
who can relate bad air quality to visible distance more than
traditional parts per billion or Mg/m3(pollution).

True and accurate
visibility measurement by a nephelometer must be performed by taking wet
measurements. Wet measurements do not control humidity (by heating
sample) and include the affects of humidity, fog and their interaction
with aerosols in the visibility measurement.

National Parks

The degredation of
pollution and visibility not only harms people's health, but it also has
an economic effect on Tourism. Visibility is important for national
parks as clear skies provide more spectacular views of nature.
Monitoring this visibility is key to ensuring all visitors and tourists
recieve the best experience possible, and eliminating any threats to
this. One of the main programs designed to monitor visibility at
national parks is the I.M.P.R.O.V.E. program (http://vista.cira.colostate.edu/improve/)

Air port visibility

Visibility monitoring at
airports is vital for aircraft landing and the safety of passengers.
Nephelometers have been shown to provide an accurate, real-time
measurement of visibility. The Nephelometer’s strength in this
department is found in its wet mode of operation; this mode doesn’t heat
the sample and combines both the effects of haze, smog and fog within
its calculation.

Nephelometers use in
airports has been cited in numerous publications for their use in
Airport visibility, one of the most important ones is stated below:

"The planned transition
from human to automated airport visibility monitoring has unfortunate
implications for visibility monitoring. Most of the existing information
about historical haze trends is from airport data. The new automated
instruments are designed to measure the very poor visibility conditions
that are of primary concern for aviation safety, but will provide little
or no more information on haze under typical visibility conditions. We
recommend that the proposed instrumentations be supplemented with
integrating Nephelometer which would permit measurement of light
scattering coefficients under visibility conditions. The addition of
Nephelometers to airport instrumentation would ensure that haze levels
are monitored over a broad and representative geographic scale, thereby
providing important information on spatial & temporal trends of
regional haze."

Page 140 "Protecting Visibility in National Parks and Wilderness Areas"